Leaving CanadaOn their way to Mexico, these monarchs were resting on the north shore of Lake Erie:

"Over 3000 monarchs are roosting in Wainfleet, Ontario. The butterflies have been increasing over the past few days, as wind conditions were not favourable. Thursday's forecast is clear, warm and with a northeast wind, so the butterlies will be making their journey in the morning. What a sight it will be."

Roosts reveal where large numbers of monarchs are concentrated. This fall's migration is unusual, with large numbers in the east and small numbers in the Central Flyway. Does this pattern mean fewer monarchs will make it to Mexico?